Ciera Kotaska
NDSU Extension Agriculture and Natural Resources Agent - Wells County
North Dakota State University
Carrington, North Dakota, United States
Talon M. Mues, n/a
Extension Instructor
Nebraska Extension
Lexington, Nebraska, United States
Nabina Karki
Graduate Student
South Dakota State University
Brookings, South Dakota, United States
Sophia Enter, n/a
Undergraduate Research Assistant
South Dakota State University
Brookings, South Dakota, United States
Connie Strunk
South Dakota State University
Sioux Falls, South Dakota, United States
Tamra Jackson-Ziems, n/a
Primary Investigator
University of Nebraska - Lincoln
Lincoln, Nebraska, United States
Rodrigo B. Onofre, n/a
Assistant Professor, Row Crops Pathology
Kansas State University
Manhattan, Kansas, United States
Madalyn Shires, PhD
Assistant Professor and Extension Plant Pathology Specialist
South Dakota State University
Brookings, SD, USA
Phyllachora maydis is the causal agent of tar spot on corn. In 2024, an estimated 293.4 million bushels were lost across infected areas in the United States and Canada. Tar spot was first reported in the United States in 2015 and has since spread to the Great Plains, with known infection in four of the Great Plains states. The objective of this study is to determine if there is genetic diversity in the Great Plains tar spot populations, indicating adaptation to the region. Symptomatic corn leaves (n=300) were collected from Kansas, Michigan, Minnesota, Missouri, Nebraska, and South Dakota. Nucleic acids were extracted and quantified. PCR was performed with primers ITS 5/ITS 4 and V9D/LS266 and products were visualized. All positive PCR products were Sanger sequenced; sequences were aligned in Geneious Prime 2025.0.3 and analyzed for single nucleotide polymorphisms (SNP). No SNPs were present in any sequences for either primer set indicating that there is no genetic diversity present in the genome regions used in this study. Most samples were at least 90% match to the reference sequences of P. maydis in NCBI GenBank. The conclusion of this study is that tar spot in the Great Plains is likely from a single introduction event and has not had time to adapt to the region yet.